Lower Gastrointestinal Bleeding (LGIB) 

Most lower GI bleeds are self-limited, 10–15% present with severe bleeding requiring ICU management.

1. Definition

Lower GI bleeding (LGIB) refers to bleeding originating distal to the ligament of Treitz, typically from the colon, rectum, or anus.

However in critical care practice:

• Upper GI bleeding with rapid transit may present as hematochezia
• Therefore upper GI source must always be excluded first in severe bleeding

2. Epidemiology

Age distribution:

3. Important ICU Definitions

Massive Lower GI Bleeding

Usually defined as:

• >3–4 units PRBC in 24 hours
• Hemodynamic instability
• Persistent hematochezia

Severe LGIB (ACG definition)

Presence of:

• SBP <100 mmHg
• HR >100
• Hb drop ≥2 g/dL
• Need for transfusion ≥2 units

4. Clinical Presentation

Hematochezia

Passage of bright red blood per rectum

Causes:

• Distal colon bleeding
• Massive upper GI bleeding

Maroon stools

Suggests right colon or small bowel bleeding

Melena from lower source

Rare but possible in right-sided colon bleeding

5. Causes of Lower GI Bleeding

5.1 Diverticular Bleeding (Most common)

• 30–50% of LGIB
• Arises from vasa recta erosion in diverticulum

Characteristics:

• Sudden painless hematochezia
• Often large volume
• Usually stops spontaneously

Risk factors:

• Age
• NSAIDs
• Antiplatelets
• Anticoagulants

5.2 Angiodysplasia

Degenerative vascular malformations.

Typical features:

• Age >65
• Recurrent bleeding
• Right colon predominance
• Associated with:

Triad:

• Aortic stenosis (Heyde syndrome)
• CKD
• von Willebrand disease

5.3 Ischemic Colitis

Caused by hypoperfusion of colon.

Common in ICU patients.

Common risk factors:

• Shock
• Vasopressors
• Cardiac surgery
• Atherosclerosis

Typical presentation:

• Abdominal pain
• Followed by hematochezia

Most common locations:

• Splenic flexure
• Rectosigmoid

5.4 Inflammatory Bowel Disease

Includes:

• Ulcerative colitis
• Crohn disease

Bleeding due to:

• Mucosal ulceration
• Inflammation

Usually chronic bleeding but severe cases may require ICU.

5.5 Colorectal Cancer

Features:

• Occult bleeding
• Iron deficiency anemia
• Intermittent hematochezia

Massive bleeding is rare.

5.6 Hemorrhoids

Very common but rarely causes massive bleeding.

Features:

• Bright red blood
• On toilet paper
• No hemodynamic instability

5.7 Post-polypectomy Bleeding

Occurs:

• Immediate
• Delayed (5–10 days)

Important in ICU after colonoscopic procedures.

5.8 Radiation Proctitis

Occurs months to years after pelvic radiation.

Features:

• Fragile mucosa
• Telangiectasia
• Recurrent bleeding

5.9 Infectious Colitis

Common organisms:

• Shigella
• Salmonella
• Campylobacter
• EHEC
• CMV (immunocompromised)

Presentation:

• Bloody diarrhea
• Fever
• abdominal pain

6. Causes Specific to ICU

Critically ill patients have additional causes:

7. Initial ICU Assessment

Step 1: Hemodynamic evaluation

Assess:

• Airway
• Breathing
• Circulation

Signs of severe bleeding:

• Hypotension
• Tachycardia
• Altered mental status
• Oliguria

Step 2: Large bore access

Insert:

• 2 large bore IV cannulas
• Arterial line if unstable
• Central line if massive transfusion expected

Step 3: Resuscitation

Fluid:

• Balanced crystalloids initially

Blood transfusion:

Target Hb:

Step 4: Massive transfusion protocol

If severe hemorrhage:

Use 1:1:1 ratio

• PRBC
• Plasma
• Platelets

8. Laboratory Investigations

Essential tests:

• CBC
• PT/INR
• aPTT
• Platelet count
• Fibrinogen
• Renal function
• LFT

Cross match:

• At least 4–6 units PRBC

9. Risk Stratification

Several predictors of severe LGIB:

Clinical predictors:

• SBP <100
• HR >100
• Syncope
• Ongoing hematochezia
• Age >60

Lab predictors:

• Hb <10
• INR >1.5
• BUN elevation

Oakland Score 

Used to identify low-risk patients suitable for outpatient management.

Oakland Score Variables

Interpretation

In ICU patients → usually >15.

10. Rule Out Upper GI Bleeding

Indicators of Upper GI Source

Action

If suspicion exists → urgent upper endoscopy before colonoscopy.

11. Diagnostic Modalities

Classify patient into:

11.1 Colonoscopy (Gold Standard)

Early colonoscopy within 24 hours

Benefits:

• Diagnosis
• Therapeutic intervention

Requires:

• Rapid bowel preparation
• Hemodynamic stability

11.2 CT Angiography

Very important in ICU.

Detects bleeding rate:

>0.3–0.5 mL/min

Advantages:

• Rapid
• Non-invasive
• Identifies bleeding location

Preferred in active severe bleeding.

11.3 Conventional Angiography(Diagnostic + therapeutic)

Detects bleeding rate:>1 mL/min

Indications

• Active bleeding on CTA
• Failed endoscopy
• Ongoing massive bleeding

Allows therapy:

• Embolization
• Vasopressin infusion

11.4 Radionuclide Scan (Tagged RBC scan)

Detects very slow bleeding:

0.1 mL/min

However:

• Very sensitive but poor localization.
• Rarely used in ICU

11.5 –capsule endoscopy (CE) and deep enteroscopy (DE)

 In Lower GI bleeding evaluation, capsule endoscopy (CE) and deep enteroscopy (DE) are primarily used when standard investigations fail to identify the bleeding source, especially when small bowel bleeding is suspected. This scenario is often called obscure gastrointestinal bleeding (OGIB).

Suspect small bowel source when:

• Upper endoscopy is negative
• Colonoscopy is negative
• Persistent or recurrent bleeding
• Iron deficiency anemia with no identified source
• Ongoing transfusion requirement
• Recurrent obscure GI bleeding

Most common small bowel bleeding cause → Angiodysplasia

Capsule should be done early after bleeding episode for highest yield

Deep enteroscopy allows direct visualization and therapeutic intervention in the small bowel.Unlike capsule endoscopy, DE is invasive but therapeutic.Lesion Identified on Capsule Endoscopy commonest indication of Deep enteroscopy

12. Endoscopic Therapy

Common techniques:

Most effective for:

• Diverticular bleeding
• Angiodysplasia

13. Interventional Radiology

Used when:

• Endoscopy fails
• Ongoing bleeding
• Hemodynamic instability

14. Surgical Management

Indications:

• Failure of endoscopy + embolization
• Persistent massive bleeding
• Hemodynamic instability

Procedures:

• Segmental colectomy
• Subtotal colectomy (if source unknown)

15. Management of Anticoagulant / Antiplatelet Drugs

16. Complications

Severe LGIB may lead to:

• Hypovolemic shock
• Acute kidney injury
• Myocardial ischemia
• Transfusion reactions
• Bowel ischemia after embolization

17. Prognostic Factors

Poor outcomes associated with:

• Age >70
• CKD
• Liver disease
• Anticoagulants
• Persistent bleeding
• Need for >4 units PRBC